ABSTRACT Young Black women (YBW) between the ages of 18 to 24 have higher rates of HIV than any other age or race and ethnicity group of women in Los Angeles County. Social networks of YBW could be both protective and risky via social influence and sexual-health-related communication. Yet there is a dearth of literature on YBW and their social network members (SNMs), particularly regarding how social networks can be used for HIV prevention and treatment. With the current HIV/AIDS priorities of decreasing incidence of HIV and increasing the use of preexposure prophylaxis (PrEP) among high-risk groups, examining YBW and their social networks is essential in understanding how to use these networks to implement preventive interventions such as PrEP among high-risk YBW. The proposed two-year Ruth L. Kirshstein NRSA study seeks to reduce HIV/AIDS incidence among YBW aged 18?24 by investigating condom use, HIV testing, and knowledge and perceptions of PrEP as tools to prevent HIV among YBW. To achieve this goal, the proposed study will examine 200 YBW and their SNMs to explore YBW?s social media usage and its association with sexual risk and protective behaviors (i.e., HIV testing, condom use, and interest in PrEP) among YBW (Aim 1); identify subgroups profiles of YBW based on individual- and social-network-level risk factors and investigate whether HIV testing, condom use, and interest in PrEP are key indicators of those subgroups (Aim 2); and investigate whether social network and SNM characteristics are associated with HIV testing, condom use, and interest in PrEP among YBW (Aim 3). Preliminary results from the proposed PI?s pilot study examining 78 YBW women and their SNMs (n = 1,068) revealed that YBW spoke to approximately 55% of their SNMs about sex, 32% about condoms, and 21% about testing for HIV. Additionally, individual-level descriptive statistics revealed that a majority of these women were sexually active (85%), yet very few of the sexually active women used condoms during their last sexual activity (vaginal or anal sex; 19.7%, n = 13). Furthermore, 76% of the women in the study had not heard of PrEP. After a brief description of PrEP, 47% of the YBW reported being interested in taking PrEP as a tool for HIV prevention. Due to the small sample size of YBW (n = 78), there was not enough power in the pilot study to examine associations at the individual level (i.e., condom use, HIV testing, and interest in PrEP). More importantly, individual-level risk-taking behaviors could not be correlated with network variables. Thus, these pilot study data are not sufficient to address the current aims of the proposed study. This proposed study will address these individual-level limitations by recruiting 200 YBW. Findings from this study will provide insight regarding factors not typically examined, such as YBW?s knowledge and perceptions of PrEP and the association of their social networks, HIV risk behaviors, and social media use with condom use, HIV testing, and interest in PrEP.